A conventional speed reducer may comprise a casing, a high speed shaft connecting to an eccentric rod having a plurality of different, hollow pinion rollers, a plurality of low speed shaft pins rotatably disposed in the pinion rollers respectively and each having one end opposite to the high speed shaft and connected to the low speed shaft, a gear roller retaining ring mounted on the pinion rollers for confining the pinion rollers, and a plurality of ring gear pins each enveloped with a ring gear roller for rotatably engaging with the hollow pinion rollers and each having both ends connecting to an inner surface of the casing. Rotation of the eccentric rod rotates the pinion rollers about the ring gear pins to actuate the low speed shaft pins so as to rotate in the pinion rollers for speed reduction.
However, the conventional speed reducer needs an output shaft so that it needs many elements, the structure is complicated and the total thickness is thicker. It is hard to meet the request of thinning market.
Furthermore, the ratio of reducing speed is not increased. If the reducing speed needs to be increased, the volume needs to be increased. The cost is hard to reduce. Thus, the need for improvement still exists.
In view of the foregoing circumstances, the inventor has invested a lot of time to study the relevant knowledge, compare the pros and cons, research and develop related products. After quite many expetireents and tests, the “speed reducer with rollers” of this invention is eventually launched to improve the foregoing shortcomings, to meet the public use.